PARIS - Salty water just below the surface of Mars could hold enough oxygen to support the kind of microbial life that emerged and flourished on Earth billions of years ago, researchers reported Monday (Oct 22).
In some locations, the amount of oxygen available could even keep alive a primitive, multicellular animal such as a sponge, they reported in the journal Nature Geosciences.
"We discovered that brines" - water with high concentrations of salt - "on Mars can contain enough oxygen for microbes to breathe," said lead author Vlada Stamenkovic, a theoretical physicist at the Jet Propulsion Laboratory in California.
"This fully revolutionises our understanding of the potential for life on Mars, today and in the past," he told AFP.
Up to now, it had been assumed that the trace amounts of oxygen on Mars were insufficient to sustain even microbial life.
"We never thought that oxygen could play a role for life on Mars due to its rarity in the atmosphere, about 0.14 per cent," Stamenkovic said.
By comparison, the life-giving gas makes up 21 per cent of the air we breathe.
On Earth, aerobic - that is, oxygen breathing - life forms evolved together with photosynthesis, which converts CO2 into O2. The gas played a critical role in the emergence of complex life, notable after the so-called Great Oxygenation Event some 2.35 billion years ago.
But our planet also harbours microbes - at the bottom of the ocean, in boiling hot springs - that subsist in environments deprived of oxygen.
"That's why - whenever we thought of life on Mars - we studied the potential for anaerobic life," Stamenkovic.
LIFE ON MARS?
The new study began with the discovery by Nasa's Curiosity Mars rover of manganese oxides, which are chemical compounds that can only be produced with a lot of oxygen.
Curiosity, along with Mars orbiters, also established the presence of brine deposits, with notable variations in the elements they contained.
A high salt content allows for water to remain liquid - a necessary condition for oxygen to be dissolved - at much lower temperatures, making brines a happy place for microbes.
Depending on the region, season and time of day, temperatures on the Red Planet can vary between minus 195 and 20 deg C.
The researchers devised a first model to describe how oxygen dissolves in salty water at temperatures below freezing.
A second model estimated climate changes on Mars over the last 20 million years, and over the next 10 million years.
Taken together, the calculations showed which regions on the Red Planet are most likely to produce brine-based oxygen, data that could help determine the placement of future probes.
"Oxygen concentrations (on Mars) are orders of magnitude" - several hundred times - "greater than needed by aerobic, or oxygen-breathing - microbes," the study concluded.Cloudsteppers by Clarks Sillian Bella Shoes - Women's Size 10W - Grey (DAMAGED)Womens Clarks Bendables Leather Slip On Loafers Shoes 7.5 WNaturalizer Natural Tan Leather Basket Weave Loafer`s Women`s 8 M**Propet TravelActiv Mary Jane Shoe - Women's Size 8D - GrayCall It Spring Women's Fibocchi Ballet Flat Navy Miscellaneous 5 MLadies Girls Lolita Shoes Faux Leather Bow Sweet Vintage Japanese Cosplay Black , Cole Haan Grand.OS Womens Tali Ballet Flat Gold Leather Shoes size 6.5 M work , CLIF Paris Made in Italy 'Marie' Ballet Flats Shoes Brown Leather Size 36 , Dansko 41 Mary Jane sandal camel , Rieker Slippers Ballerinas Leather Leather Insole Pepper NEWJoan & David 'Dafaline2' Gold/Sequinned Womens Loafers Size US 7M NewWomen's Skechers Go Walk 4-PURSUIT - Navy/Grey - New in Box!Born Walking Shoes Womens Size 6.5 Dark Brown Leather Oxfords - 37 EURCole Haan Brown Leather Womens Loafer Shoes Size 7.5 B Tensile Air Slip On Italy , Cobb Hill Women's Penfield Cutout Mary Jane Flat, Black, Size 9.5 qAxZ , Women's Skechers Gray Flat Working Shoes Sneaker US7 UK4 EUR37 , Ed Hardy Designs shoes Mermaid Serpent Koi Fish ART Womens Sz 10 Sneakers PurplePropet Women Billie W5100 Light weight Walking Sneaker Shoes WHITE TURQUOISE 7MNEW Women Fashion Shoes Sneaker Boots Wedge Heel High Top Shoe Suede PU Sz5.5-10Demonia Women's Creeper 302 Wedge OxfordRyka Devotion Walking Shoes - Women's Size 7.5M, Gray/Pink/LimeSKECHERS charcoal gray & black suede athletic shoe 9.5M new without box , Nike Womens Air Pegasus '89 Red Fashion Sneakers Shoes 5 Medium (B,M) BHFO 3824 , Under Armour Womens UA Speedtire Ascent Mid Running Shoe, Bayou Blue, 8.5 M USJessica Simpson Women's FitT Walking ShoeNew Balance Women's 300 'Summer Utility' in Slate Blue WRT300U BNIB Free Ship , New Balance Fresh Foam 980 Running Shoes Sz 9 D Wide Blue Womens 2D1 , ASICS Womens - Blue Running Shoes Size 7.5 (367086) , Men Running Shoes Athletic Black Sneakers Walking Light Sports Male Shoes ONEMIXNEW Converse Chuck Taylor 556634C Shoreline Women's Sneakers 6 M IN BOX
"Our results do not imply that there is life on Mars," Stamenkovic cautioned. "But they show that the Martian habitability is affected by the potential of dissolved oxygen."